From: Dongli Zhang dongli.zhang@oracle.com
commit 88d724e2301a69c1ab805cd74fc27aa36ae529e0 upstream.
When a CPU goes offline, the interrupts affine to that CPU are re-configured.
Managed interrupts undergo either migration to other CPUs or shutdown if all CPUs listed in the affinity are offline. The migration of managed interrupts is guaranteed on x86 because there are interrupt vectors reserved.
Regular interrupts are migrated to a still online CPU in the affinity mask or if there is no online CPU to any online CPU.
This works as long as the still online CPUs in the affinity mask have interrupt vectors available, but in case that none of those CPUs has a vector available the migration fails and the device interrupt becomes stale.
This is not any different from the case where the affinity mask does not contain any online CPU, but there is no fallback operation for this.
Instead of giving up, retry the migration attempt with the online CPU mask if the interrupt is not managed, as managed interrupts cannot be affected by this problem.
Signed-off-by: Dongli Zhang dongli.zhang@oracle.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Link: https://lore.kernel.org/r/20240423073413.79625-1-dongli.zhang@oracle.com --- kernel/irq/cpuhotplug.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c index 367e15a2f570..eb8628390156 100644 --- a/kernel/irq/cpuhotplug.c +++ b/kernel/irq/cpuhotplug.c @@ -130,6 +130,22 @@ static bool migrate_one_irq(struct irq_desc *desc) * CPU. */ err = irq_do_set_affinity(d, affinity, false); + + /* + * If there are online CPUs in the affinity mask, but they have no + * vectors left to make the migration work, try to break the + * affinity by migrating to any online CPU. + */ + if (err == -ENOSPC && !irqd_affinity_is_managed(d) && affinity != cpu_online_mask) { + pr_debug("IRQ%u: set affinity failed for %*pbl, re-try with online CPUs\n", + d->irq, cpumask_pr_args(affinity)); + + affinity = cpu_online_mask; + brokeaff = true; + + err = irq_do_set_affinity(d, affinity, false); + } + if (err) { pr_warn_ratelimited("IRQ%u: set affinity failed(%d).\n", d->irq, err);